Protective device for electric circuits.



PATENTED AUG. 18, 1907.

T. I. JEFPRIES. PROTECTIVE DEVICE FOR ELECTRIC CI RCUITS.

APPLICATION FILED NOV. 22. 1904.

IINEHTOTI hzmm's [Jeff/"I53. by m ax I THOMAS I. JEFFRIES,

OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR TO STANLEY ELECTRIC MANUFACTURINGCOMPANY, OF PITTSFIELD, MASSACHUSETTS, A CORPORATION OF NEW- JERSEY;

Specification of Letters Patent.

PROTECTIVE DEVICE FOR ELECTRIC CIRCUITS.

Patented Aug. 13, 1907.

Application filed November 22,1904:- Serial No. 233.812.

To all whom it may concern:

Be it known that 1,.TlIOMAS I. .Inrrmns, acitizen of the United States,residing at Pittsfield, in the county of Berkshire and State ofMassachusetts, have invented certain new and useful Improvements inProtective Devices for Electric Circuits, of which the following is aspecification.

My invention relates tection of electric circuits.

It is ordinarily necessary; to protect electric circuits against theflow of too great an amount of current there in, and iorthis purpose amagnet coil is ordinarily provided arranged to open a switch in thecircuit whenever the current reaches a dangerous amount. On somecircuits on which a temporary overload is likely Y to occur at frequentintervals, it is inconvenient ii the circuit-breaker operates for eachof these overloads. It

has been customary, heretofore, in such cases to pro vide what is knownas a time-limit circuit-breaker with v j proposed heretoiore tosupplement the time-limit tripa movable member, controlled by thetrip-coil, provided with retarding means, so that an overload of acertain duration is required to effect the operation of thecircuit-breaker. Such time-limit devices are, however, sometimes asource of danger, since, ii a very heavy over-load occurs, it isdesirable that the circuit should be opened immediately.. It hasconsequently been ping-coil or relay with a second coil, withoutretarding devices, so proportioned as to operate only on excessiveover-loads. r

My invention consists in arranging a single coil so that it controls twomovable members, one arranged with a time-limit device, and the otherwithout. Thus, a single coil takes the'place of the two coils which havebeen sometimes employe'd heretofore.

More specifically considered, my invention consists in the combinationwith a single coil of two magnetic members arranged in; series in themagnetic circuit of the coil, one of the members provided with retardingmeans, and the other member without retarding means but arranged torespond only to a much heavier current in the magnet coil than isrequired to produce a move ment of the first member.

My invention will best be understood by reference to the accompanyingdrawings, in which Figure 1 shows a magnetically-operated relay arrangedin accordance with my invention, and Fig. 2

I shows a diagram of the circuit connections.

In Fig. 1, A represents the magnet coil, which is provided with amagnetic casing B partially surrounding the coil. O represcnts a movablecore which is shown as of the ordinary type, and which is connected atits lower end to a dash-pot D. The core O carries the intomagnetic-relays for the prois normally held in the position shown bygravity or by a spring. When a predetermined current-flowpasses throughthe coil A, the core 0 starts to move upwards,

but this motion is retarded by the dash-pot D, so that the contactmember E does not engage the stationary contacts e e, until apredetermined time has elapsed.

' lithe overload has meanwhile ceased, the core C drops back to theposition shown, without bringing the member E into engagement with 'thestationary contacts. F represents a second movable magnetic member whichis included, in series with the core 0 and the casing B, in the magneticcircuit of the coil A. The member F is normally held against the stopsff, as shown, by the tension-spring G, and this spring is soproportioned that the magnetic pull upon the member F is not strongenough to move it downward away from its stops, unless the coil A istraversed by a current corresponding to a heavy overload in the circuitto be protected. The member F will consequently remain stationary on anordinary overload, which cause the core C to start on its-upwardmovement; but in case a very heavy overload occurs, the member F will beinstantly drawn down, bringing the insulated contact member H intoengagement with the stationary contacts h h.

The contacts 0 e and h h are connected in parallel in the controlcircuit, as is shown in Fig. 2. From Fig. 2 it will be seen that iteither contacts e e-or contacts h h are electrically connected, bytheirrespective contact members E or H, a circuit will be closed through thebattery I, and trip-coil J on the circuit-breaker K, which is connectedin the same circuit with the magnet coil A. The operation of eithermovable member C or F, as has been described above, will thus result inopening the circuit to be protected.

I do not desire to limit myself to the particular construction andarrangement of parts here shown, but

aim in the appended claims to cover all modifications which are withinthe scope ofmy invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

1 In combination with a circuit to be protected, a magnet windingenergized from said circuit, two independently-movable memberscontrolled by said winding and responsive to different overload currentstrengths therein, means for retarding the movement of the memberresponding to the'smaller current flow, a switch in said circuit, andconnections between both of said members and said switch operative uponthe effective overload movement of either of said members to open saidswitch.

2. In combination with a circuit to be protected, a magnet windingenergized from said circuit, two independently-movable memberscontrolled by said winding and responsive to different. currentstrengths therein, means for retarding the movement of the memberresponding to the smaller current-flow, relay contacts carried by saidmembers, a switch in'said circuit to be protected, and a trip magnet forsaid switch in circuit with the relay contacts, carried by both of saidmembers.

3. In combination with a circuit to be protected,. a magnet windingenergized from said circuit, two independe'ntly-movable magnetic membersincluded in series in the magnetic circuit of said winding andresponsive to difierent current strengths therein, means for retardingthe movement of the member responding to the smaller current flow, relaycontacts carried by said members, a switch in said circuit to beprotected, and a trip-magnet for said switch in circuit with the relaycontacts carried by both of said members. I

4. In combination with a circuit to be protected, a' magnet windingenergized from said 'circuit, two independ ently movable memberscontrolled by said winding and responsive to different current strengthstherein, a switch in said circuit to be protected, means controlled bythe movable member responsive to the small current flow in said magnetwinding. for opening said switch after a definite time interval, andmeans controlled by the movable member responsive to the greater currentflow for opening said switch instantaneously.

In witnesswhereof, I have hereunto set my hand this first day ofNovember, 1904.

' THOMAS l. .TEFFRIES. Witnesses SAMUEL E. WInmrInLn, JAMES E. FLYNN.

